Wireless communication systems, such as cellular telephone systems, have proved to be very popular. Such systems typically include numerous mobile units (e.g., cellular telephones), a plurality of base stations at fixed locations, and one or more switching centers connecting the wireless communication systems to other communications systems, such as the land line public switched telephone network.
It is common for such systems to employ a large number of discrete communication channels for communicating voice and data from one location to another and for controlling system functions. It is also common for there to be multiple communications service providers in competition with each other for each type of communication service. Further, within a given geographical area, it is typical for the various communication channels to be allocated to the different competitors such that only one service provider is responsible for providing service on any given channel.
To facilitate communications channel allocation, the spectrum of channels may be divided into several channel bands, each containing a plurality of communications channels. Thereafter, an entire channel band is typically allocated to a particular service provider for a given geographic region. Thus, in a certain region, service provider Alpha may be allocated channel bands A and C, while service provider Beta may be allocated channel band B, and service provider Gamma all other channel bands. The particular details of the channel band allocations are well known in the industry.
During use, it is common for the mobile unit to initiate a band scan in order to locate an appropriate control channel. The band scan is a process by which a mobile unit searches through channels in a channel band, looking for an appropriate control channel to camp on. A band scan could be initiated for a wide variety of reasons, including at power-up, at call release, or when a control channel is lost. In some instances, multiple band scans are run back-to-back on different channel bands in what is called a wide-band scan. Because the band scanning process takes time and otherwise utilizes system resources including mobile unit power, it is very desirable for the band scan or wide-band scan to happen as quickly as possible.